Fan



March 26, 1929. F. w. HOLMES 1,706,608

FAN

Filed Aug. 5, 1927 F WHOLMES Gbtozwu Patented Mar. 26', 1929.- i I I j UNITED STATES PATENT OFFICE.

FRANK W. HOLMES, O15 CHICAGO, ILLINOIS.

Application filed August 5, 1927. Serial No. 210,979.

This invention relates to fans and more particularly to exhaust ventilatlng fans.

An important object of to provide a fan the invention is which is adapted to project he velocity of which is substantially constant throughout its crosssectional area.

A further object is to provide a novel blade which is adapted to project air at a substantially constant velocity throughout its length.

A further object is to provide a blade which is graduated in width and pitch in such a manner as to compensate for the and thus varying linear speeds throughout its length discharge fluid from its lnner portions at substantially the same speed as from its 'outerportions.

A further object is to provide a fan blade having the inner portion thereofpro eeting in the direction of rotation to intercept a greater quantity of air than will be intercepted by the outer portion of the blade,

thus compensating tative speeds of the inner ortions.

A further object is to for the varying linear roand outer blade provide a blade which is pitched throughout its length, the

pitch of greater compensate for the tativespeeds.

A further object is to pr than that of the which is convexed throughout its length width to more eflic'iently is operating of the fluid will be disfluid in which it greater quantity e inner portion of the blade being outer portion to differences in linear roovide a fan blade and pocket the whereby a charged by a fan of a given size.

A further object is to provide a fan of the character referred to the rear edges of the blades of which are ranged in a plane substantiall straight and arat rightangles to the axis of rotation to e ect a more eflicient discharge f the fluid. Other objects and advantages of the, in-

vention will become apparent during the course of the following description.

In the drawings I have shown one embodiment of the invention.

Figu

In this showing,

re 1 is a rear face view,

Figure 2 is an edge elevation,

Figure 3 is a front face Figure 4 is a detail sec of Figure 1,- and,

view,

tion on line 4-4 Figure 5 is a similar view on line 5-:5 of Figure 1.

Referring to the drawings, the numeral designatesa suitable hub adapted to be mounted upon a drive shaft and provided with a plurality of projections 11 to each of which a blade indicated as a whole by the numeral 12 may be attached by rivets or the like 13. In the present instance the blades are indicated as being provided with projections 14 at their inner ends which lie against the rear face of the propeller and are secured thereto by screws 15 passing through a plate 16. While the blades have been described as being formed separate it will be from the hub and attached thereto, be apparent that these elements 'may made integral if desired.

substantially at right angles to the axis of air, or other fluid may 8 rotation. Thus the be discharged from the fan in the common plane referred to. The forward edge of each blade is inclined in the direction of rotation whereby the outer portion of each blade increases in width toward its inner end. For substantially half its radial length, the forward edge of each blade projects sharply in the direction of rotation as indicated at 21 to intercept a greater portion of the fluid in which the blade is operated.

The outer edge 22 of each blade is pitched as indicated in Figure 2 and the pitch of the blade gradually increases toward its inner end as indicated at 23.

The operation of the device is as follows:

It will be apparent that any number of apparent that the projecting forward edges 21, arranged in advance of the other portions of the blades,

intercept the greater proporthat each fan be provided with tion of the fluid in which the fan is' operated. As previously stated, the pitch ofthe inner portion of each blade is greater than that of the outer portion, and the greater width and pitch of the inner portions of the blades serve to compensate for the decreased linear rotative speeds at the inner portions of the blades. The greater radial convexity of each blade occurs adjacent the inner portion thereof, and this .portion also is arranged slightly in advance of the remainder of the blade with respect to the direction of travel of the fluid, as indicated in Figure 5. This structure also serves to compensate for the var in linear s eeds of the inner and outer portions of the blades. The sharply convexed inner portion of theblades shown in Figure 5 tends to prevent any inward slipping of the fluid from the central portion of the blade resulting from the greater quantity of fluid intercepted thereby, while the radial curvature of the outer portion of each blade in the direction of discharge of the fluid tends to overcome centrifugal force and thus prevent outward slipping of the fluid. The fan resulting from the, combination of the various structural features referred to is adapted to operate in such a manner as to discharge a column of fluid substantially parallel to the axis of rotation, the linear speed of the inner portion of the column being substantially squal to that of the outer portion. Eddy currents in the resultant fluid column, which would tend to reduce the velocity of the column are substantially eliminated, by forming the blades wit straight rear edges arranged at right angles to the axis of rotation.

The characteristics .of the fan, as above outlined, render it particularly adapted for use as'a ventilating fan, but it will be apparent that the device also is readily adapted for use as a propeller and possesses a high degree of efficiency due to the direction of discharge of the fluid and the uniform velocity thereof.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. A fan blade comprising a body having its forward face concaved transversely thereof and having its forward edge projecting in the direction of rotation and at the end of the body adjacent the axis of rotation, said body having its forward face concaved having its forward face concaved transversely thereof and'having its forward edge projecting in the direction of rotation and at the end of the body adjacent the axis of rotation, said body having its forward face concaved throughout its length with the greatest concavity lying adjacent the inner end of the body, the pitch of said body progressively increasing toward its inner end for substantially half its radial length and then sharply increasing to a point adjacent its widest portion.

4. A fan blade comprising a pitched body having its forward face concaved transversely thereof and having its forward edge projecting in the direction of rotation and at the end of the body adjacent the axis of rotation, said body being curved rearwardly for substantially half its radial length and then forwardly to its outer extremity, the.

pitch of said body progressively increasing towardits inner end'for substantially half its radial length and then sharply increasing to a point adjacent its Widest portion.

. 5. A fan comprising a hub, a plurality of blades carried by said hub, each of said blades having. its forward face concaved transversely thereof arid having its forward edge projecting in the direction of rotation and at the end of the blade adjacent the axis of rotation, each blade having its forward face concaved throughout its .length with the greatest concavity lying adjacent, the inner end of the blade.

6. A fan comprising a hub, a plurality of blades carried by said hub, each of said blades having its forward face concaved transversely thereof and having its forward edge projecting in the direction of rotation and at the end of the blade adjacent the axis of rotation, each blade being curved rearwardly for substantially half its radial length and then forwardly to its outer extremity.

Intestimony whereof I aflix my signature.

-- FRANK W: HOLMES. 

